After languishing for years in the shadows of psychiatry's definition of adult depression, irritability is finally getting some respect again. It's about damned time, you might say.

A new study has found that people suffering a major depressive episode who report they have become grouchy, hostile, grumpy, argumentative, foul-tempered or angry will likely have a "more complex, chronic and severe form" of major depressive disorder than those who do not acknowledge irritable feelings and behavior.

We're not talking about a small minority of the depressed either: In this 30-year study of 536 subjects who first presented with depression, 54% acknowledged irritability in feelings and behavior. And while cussedness is increasingly recognized as a hallmark of depression in men, the current study found that a majority of women fell into its "irritable" group as well.

Compared with the merely sad, guilt-ridden and lethargic, the irritable depressed had more severe depressive symptoms. They stayed depressed for longer. They relapsed more readily. And they were more likely to experience other psychiatric conditions as well, including anxiety and substance abuse disorders, impulse-control problems and antisocial behavior, the study showed.

The difference between the two groups was so stark as to suggest that major depression with "overt irritability/anger" might be diagnosed and treated as a distinct form of the disorder, requiring more intensive treatment, the authors wrote.

Indeed, the researchers suggested, such depression may spring from different biological origins than depression in which manifestations of anger or irritability are absent. That is also suggested by the study's finding that subjects expressing irritability were more likely than those who did not to have a family history of bipolar disorder.

The latest research, published in the journal JAMA Psychiatry, began in 1978 to track 536 adult Americans in five U.S. cities who were seeking help for an episode of major depressive disorder. Researchers interviewed subjects about their symptoms twice a year for the first five years and at least once a year thereafter for an average of more than 16 years. More than 45% of the subjects were followed for 20 or more years, giving researchers an unusually detailed perspective on the long-term course of depression.

The study's authors did not count those who said they experienced "occasional snappiness" among the depressed and irritable. To be counted in that group, a subject was required to acknowledge he or she was "somewhat argumentative and quick to express annoyance," that he or she "often shouts or loses temper" or that he or she "throws things, breaks windows, or is occasionally assaultive." In the most extreme manifestation of irritability, a subject would be "repeatedly violent against things or people."

Irritability is formally seen as a hallmark of major depressive disorder in children and adolescents. But in 1987, the American Psychiatric Assn. dropped it as a diagnostic criterion of major depressive disorder in adults.